KEMBOY, favourite with several firms for the Ladbrokes Trophy, will miss Saturday's big race.
The Willie Mullins-trained chaser was left stranded in Ireland after adverse weather conditions lead to the cancellation of the ferry due to ship him to the UK.
The progressive six-year-old had been as short as 4-1 for the £250,000 feature at Newbury.
The gelding had comfortably won the Grade 2 Clonmel Oil Chase on his latest outing over fences.
In Kemboy's absence, 13 runners will go to post for the race formerly known as the Hennessy Gold Cup, with Elegant Escape, Thomas Patrick and Ms Parfois now vying for outright favouritism.
Steve Massey, racing manager for owners Supreme Horse Racing Club, said: "It's obviously very disappointing.
"We were looking forward to having a horse with a leading chance in such a prestigious race, but we can't do anything about the weather.
"The ferry was cancelled this morning and the ferries later tonight could be delayed.
"Even if he did get a ferry late, he could have a rough trip and might not get to Newbury until the early hours of the morning.
"It's a big blow and disappointing for all his owners, but we know he's an exciting horse and we have to do what is in his best interests."
There were fears that another big Irish challenger in Samcro, who is heading to Newcastle for the Fighting Fifth Hurdle, could also be stuck in Ireland.
However, he was able to catch a ferry and is en route to the North East track.